嵌岩灌注桩竖向荷载传递特性现场试验

Field test on vertical load transfer characteristics of rock-socketed pile

为探讨不同桩径、不同桩长的旋挖成孔嵌岩灌注桩在不同荷载水平下的荷载传递规律,基于印尼某燃煤电站桩基工程,在6根嵌岩桩桩身安装钢筋应力计进行单桩竖向抗压静载试验。试验结果表明:6根试桩的荷载—位移(Q-s)曲线均为缓变型,没有明显的陡降段,桩顶沉降与桩顶荷载呈非线性关系,回弹率介于37.6%~70.9%之间,残余沉降较小,承载力较高,均满足设计要求;桩身轴力随深度逐渐衰减;随桩顶荷载增加,桩侧摩阻力发挥表现出异步性,最大荷载作用下嵌岩段侧摩阻力达到峰值,6根试桩在嵌岩段的最大侧摩阻力介于136.2~166.4 kPa之间;桩端阻力随荷载水平的增加逐渐增大,在最大荷载作用下,桩径为800 mm的试桩长径比介于19.38~20.13,其桩端阻力分担荷载介于54.8%~55.2%,表现出摩擦端承桩的特性;桩径为600 mm的试桩长径比介于42.17~44.67,其桩端阻力分担的荷载介于30.9%~32.6%,侧摩阻力发挥主要作用,表现出端承摩擦桩特性。试验结果对印尼地区嵌岩灌注桩的应用具有重要意义。

In order to investigate the load transfer law of rock-filled piles with different diameters and different pile lengths under different load levels,a single pile vertical compression and static load test was carried out on six rock-socketed piles installed with a steel bar stress gauge in a pile foundation project of a coal-fired power station in Indonesia.The test results show that the load-displacement(Q-s)curves of the six test piles are all slowly variable,and there is no obvious steep descending section.The pile top settlement has a nonlinear relationship with the pile top load,and the rebound rate is 37.6%~70.9%.And the residual settlement at the pile end is small,the bearing capacity of the test pile is higher than the design requirements.The axial force of the pile body gradually decreases with depth;with the increase of the pile top load,the side frictional resistance of the pile shows the asynchrony.The side friction resistance of the embedded rock section reaches its peak value under the maximum load,and the maximum side frictional resistance of the six test pile rock-socketed sections are between 136.2 kPa and 166.4 kPa.The resistance of the pile end gradually increases with the increase of the load level.Under the maximum load,the length-to-diameter ratio of the test pile with a diameter of 800 mm is between 19.38 and 20.13,and the load sharing load at the pile end is between 54.8%and 55.2%,which shows the characteristics of the friction end-bearing pile.The length-to-diameter ratio of test piles with a diameter of 600 mm is between 42.17 and 44.67,and the load sharing at the pile end resistance is between 30.9%and 32.6%.The side friction resistance plays a major role,showing the characteristics of the end-bearing friction pile.The test results are of great significance for the application of rock-socketed piles in Indonesia.